The invention relates to a fastening apparatus for a limit stop element of an electric hand tool, in particular a hand circular saw, having a guide, into which the limit stop element can be inserted and along which it can be displaced, and a locking mechanism, which can lock the limit stop element in the displacement direction.
To precisely guide a hand tool, for example to be able use a hand circular saw to execute a cut that runs as straight and as parallel to an edge as possible, these tools have a parallel guide with a limit stop element, which can be applied to a guide edge, e.g., an edge of the workpiece being processed, and can be guided along the edge. Such a limit stop element allows the angle and the distance to a guide edge to be adjusted preferably in a continuously variable manner. A fastening apparatus for such a limit stop element is provided on the hand tool, which makes a stable fixation of the limit stop element on the hand tool possible.
Fastening apparatuses that have been used until now for such a limit stop element have a guide, into which a rail-like limit stop element is inserted and along which guide displacement can occur. Normally a screw is provided for fixing the rail, which presses the rail against the guide and thereby clamps it between the screw and guide. The disadvantage of fixation with a screw is that with inadequate maintenance, contamination or with high tightening forces, detaching the screw and thus the fastening apparatus is hampered. This problem is compounded by the often small dimensions of the screw head, which requires a great manual force in order to grasp the screw and unscrew it. In extreme cases, loosening the screw without a tool is not possible. Furthermore, the screws get lost easily.
The object of the invention is creating a fastening apparatus of the type mentioned at the outset which makes it possible to adjust the limit stop element with low operating forces quickly and without tools.
According to the invention, this is achieved in the case of a fastening apparatus of the type mentioned at the outset in that the locking mechanism has a spring element, which, in its locked position, clamps the limit stop element preferably with a clamping force directed against the limit stop element and, in a released position, permits a displacement of the limit stop element. The locking is thus accomplished not by a screw, but by a spring element, which, in a locked position, clamps the limit stop element. To change the position of the limit stop element, the spring element is moved against the spring force into the released position, thereby overriding the locking of the limit stop element. After the correct position is adjusted, the spring element is released so that it automatically returns to the locked position. As a result, firstly, quick locking of the limit stop element is possible thereby reducing the danger that the limit stop element will be displaced again after the correct position has been adjusted. Secondly, adjustment of the limit stop element without tools is a given.
The clamping force is preferably aligned essentially perpendicular to the displacement direction of the limit stop element so that there can be no adjustment of the position of the limit stop element by the spring element.
The spring element preferably has a recess through which the limit stop element extends. In other words, the limit stop element is guided through the spring element. As a result, first of all, the limit stop element is guided securely. And secondly, a slipping off of the limit stop element from the spring element is safely ruled out.
The clamping of the limit stop element is achieved for example in that, in the locked position, the spring element is canted with respect to the limit stop element. In other words, in the released position, it is possible for the limit stop element to be displaced in the guide in the displacement direction. In the locked position, the position of the spring element changes in such a way that the spring element is adjacent with two edges on the limit stop element, wherein the edges act on the limit stop element with opposing forces and clamp it.
The limit stop element is thus not pressed by the spring element against another, fixed component and clamped between it and the spring element, but is held exclusively on the spring element in the displacement direction.
The canting is achieved in that the recess of the spring element is a slot, whose height preferably corresponds essentially to that of the limit stop element and whose width is preferably greater than the width of the limit stop element. In this embodiment, in the locked position, the spring element is more strongly inclined to a plane perpendicular to the displacement direction than in the released position. In other words, in the released position, the projection of the recess is wider on the plane perpendicular to the insertion direction than the width of the limit stop element. The limit stop element can thus be inserted without resistance into the fastening apparatus in the displacement direction. After positioning the limit stop element, the spring element is released so that it returns to the locked position, in which the angle to the plane perpendicular to the displacement direction is greater. In this position, because of the greater angle to the plane, the width of the projection of the recess on this plane is less than the width of the limit stop element. In other words, the edges of the recess of the spring element make contact with the limit stop element and cant thereon, thereby locking the limit stop element. Thus, no moveable parts other than the spring element are necessary on the fastening apparatus so that no maintenance expense is required for the fastening apparatus.
In order to achieve a better hold of the limit stop element, the recess is limited by edges, wherein the surfaces adjacent to the edges preferably converge at a right angle, in particular to form a sharp edge. In other words, the spring element is adjacent to the limit stop element exclusively with the sharp edge, thereby increasing the contact pressing force and thus the clamping force of the spring element may be increased.
The edges are produced in particular by cutting the recess without subsequent deburring.
The spring element preferably has a mounting end as well as a freely cantilevered end. The spring element is designed in particular to be elongated. In other words, the spring element is, for example, a spring steel sheet, which is mounted on the fastening apparatus on one end and is able to spring with the freely cantilevered end.
In the locked position, this spring element is preferably arranged obliquely to the displacement direction.
A single spring element, which cants the limit stop element, makes locking the limit stop element only in one direction possible. However, if the limit stop element is moved against the displacement direction, the limit stop element can press the spring element from the locked position into the released position, whereby a releasing of the locking may occur. In order to prevent this, two spring elements are provided in a preferred embodiment, which, with respect to the displacement direction of the limit stop element, run obliquely and non-parallel to each other. In other words, the spring elements and their clamping forces act in the respective opposite directions, wherein one spring element locks the limit stop element in a displacement direction and the second spring element locks the limit stop element in the opposite direction.
The spring elements may be connected to one another to form one piece, preferably to form a U, with a base running in the direction of the displacement direction and two spring elements inclined thereto, wherein the U is designed in particular as a mirror image to a plane perpendicular to the displacement direction. The spring elements are thus configured as a single component, whereby only one common fastening is required for both. Fastening the spring elements to the fastening apparatus is thereby simplified considerably. In this case, the spring elements have the same spring stiffness so that the clamping forces of both the spring elements and thereby the holding forces are equal in both directions. Because the spring elements are designed as a U, operation is furthermore simplified, because the spring elements have to be pressed against each other to move in the released position, which is possible in a simple manner, for example, by gripping both legs of the U.
The spring elements are arranged in the displacement direction of the limit stop rail before and after the guide so that the same may be operated without limitations by the guide or other components. The spring elements may also be pressed against the guide for example, thereby additionally creating a limit stop, which prevents the spring elements from being pressed together too far.
Instead of a direct operation of the spring elements, it is also conceivable for an additional actuating element to be provided for operating the spring elements, in particular an eccentric. As a result, any arrangement of the spring elements is conceivable, for example at a better protected position within a housing. Moreover, the operating element may be constructed such that it simultaneously operates both spring elements.
In addition, according to the invention, a parallel guide is provided on an electric hand saw, with a fastening apparatus according to the invention and with a limit stop element, which is inserted into the guide and is locked in a detachable manner by locking mechanism.
The limit stop element preferably has a lower hardness than the spring element. The adjustment of the limit stop element in particular takes place in a continuously variable manner.
Additional features and details of the invention are disclosed in the following description and in the drawings to which reference is made.